The ever-evolving Blythe solar farm project in California is one more example of the paradigm shift underway within the U.S. utility-scale market. And it's headed -- and has been for awhile -- towards solar photovoltaic power.

German solar thermal power developer Solar Millennium announced Thursday that it was selling Blythe and three other projects in its pipeline to solarhybrid. The 2.25 gigawatts worth of projects will be built with solar panels and not concentrated solar power technology as originally envisioned. Concentrated solar power (CSP) harnesses the sun's heat to produce steam, which is used to drive turbines and generate electricity. PV technology uses solar cells made from silicon (or other materials) to convert sunlight into electricity.

This isn't the first U.S. project to change from solar thermal to PV in the past year. For example, TesseraSolar's Calico Solar project, which is now owned by K Road Power, was supposed to use concentrating solar thermal technology. The Imperial Valley Solar Project (another Tessera developed) was switched to PV after it was sold to AES Solar. (The Imperial Valley project is in limbo now that San Diego Gas & Electric has terminated its power purchase agreement with AES). And NRG Energy ditched a plan to build a 92-megawatt CSP plant and sell the electricity to Pacific Gas and Electric.

Under this latest deal, German-based solarhybrid will reimburse Solar Millennium for its investment in the projects. Solar Millennium also would receive a share of any profits the projects yield. This doesn't mean Solar Millennium is completely moving away from CSP. The company indicated in a recent press release that it will focus on solar thermal and hybrid power plants in Europe, Asia, North Africa and Latin America. When demand for storable solar energy begins to grow in the U.S., it will partner to develop other solar thermal projects, the company said.

The Blythe project's transformation (see timeline) illustrates how difficult it is to bring an innovative technology to market when prices for PV continue to plummet. Solar power developers that don't take advantage of the current PV market figure they're essentially throwing money away and putting their projects at risk.

Timeline:

Fall 2010: Solar Trust of America, the U.S. subsidiary of Solar Millennium, begins preliminary construction of Blythe project. Solar Trust will use HelioTrough collectors -- developed by its sister company Flagsol GmbH -- at Blythe. This parabolic trough technology involves mounting thousands of curved mirrors on the ground that concentrate sunlight onto tubes containing fluid that heat up and create high-pressure steam to turn turbines and produce electricity.

April 2011: The Energy Department offers conditional commitment to a $2.1 billion loan guarantee to build half of the 1,000 megawatt plant in California.

May 2011: Solar Trust and solarhybrid form a joint venture for the photovoltaic market. The joint company, called solarhybrid of America, will develop, build and manage utility-scale projects in North America. The two companies said at the time the joint venture would develop standalone PV and combined CSP-PV projects.

June 2011: Interior Department Secretary Ken Salazar and California Gov. Jerry Brown are on hand for a groundbreaking ceremony.

August 2011: Solar Trust announces it will switch from solar thermal technology to PV panels for the first 500 megawatts of the Blythe project. The company says it's still committed to CSP. Improved PV market conditions was the main driver of the decision to change. As a result, Solar Trust walks away from the loan guarantee, which was awarded because the company had planned to use solar thermal.